As a route towards large seasteads, we could develop a module which will link with other modules to create seasteads of any size.
One possibility could be mass produced 3 or 4 metre diameter spheres with 6 hatches to connect with up to 6 other modules, the interior will be undefined to facilitate the conversion of any sphere to any purpose.
Only a few spheres per seastead will have any kind of propulsion and/or navigation equipment, several spheres will be liquid storage tanks, some spheres will be for services like water treatment, electricity generation, frozen food storage, general food storage, other spheres will be workshops, retail shops, residential quarters, one sphere will be a crane to lift spheres up to connect with the top hatch of lower spheres to create a multi-storey seastead, each sphere would have 8 interlocking structural supports to strengthen the seastead and take the strain off the hatches.
If a sphere is damaged it can be replaced whereas with a platform-seastead the whole seastead could be compromised if part of it is damaged, also each sphere could be a life-boat if some catastrophe should occur.

Have you done the math on the strain if one end of a row of sheres is held up by two 20ft waves, and the center of the collection is hanging above the trough between the crests? And assuming each person owns their own sphere, would you trust that their sphere will not break up under such strain? When one structural support on their sphere breaks, and all the force is on the next support, will that break up your sphere too?

“Have you done the math on the strain if one end of a row of sheres is held up by two 20ft waves, and the center of the collection is hanging above the trough between the crests?”

This would be at the design stage at the same time as deciding what material the spheres will be made from, concrete, carbon composite or some other material.The seastead will grow vertically at the same time as it grows horizontally, so a seastead will have a diamond configuration, with half as many spheres below sea level as above and across, so the seastead should not be unsupported at its centre.

“And assuming each person owns their own sphere, would you trust that their sphere will not break up under such strain? When one structural support on their sphere breaks, and all the force is on the next support, will that break up your sphere too?”

I would expect most spheres will be owned by the entity running the seastead, privately owned spheres will be around the perimeter and will not threaten the seastead if one breaks up, but this eventuality should also be addressed at the design stage, the structual supports may also be designed to absorb shocks, there should be strain gauges in the supports and the sphere, monitored constantly by a microprocessor that can give an alarm when structural failure is close.

I think these spheres will be too small to be self sufficient, and therefore unlikely to be privately owned, nomadic single family seasteads.

The sphere is the strongest shape.
No 90 degree joints to fail under the weight of waves breaking against or over the structure.
When large waves break over the seastead, water can flow over and off it easier than if the seastead where made of square or rectangular modules.

Imagine a large donut. Now imagine that the donut is sliced in 12 wedges. Each wedge would be the size of a cruise ship. You could cpntract with a cruise ship manufacturer to assemble each wedge. Each wedge is a complete ship. It could function as a stand alone ship.
Each ship would attach to each other until the donut was complete. 12 cruise ship size pieces assembled into one city on the sea. 12 propulsion systems. If a wedge needed to be replaced it, you would order a new wedge and switch them out. The city could be constantly upgraded with new technologies. You could have multiple floating cities. If 2000 people lived on each wedge, thats 24000 people. If each person paid $100,000 for a spot, thats 2.4 billion dollors for construction.

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Michael, could be something like that a floating honeycomb shell concrete structure – the big proplem is not “designing it” but “financing it” and most of all, make it a feasible real estate development.. . .
You need to build seasteading on a “very different base technology” than “shipbuilding”, cruiseships operate at budget frames of USD 120 per day/passenger just check this pricelist of our caribbean ship repair operation http://cartagena.activeboard.com/t47913497/cartagena-colombia-ship-repair-pricelist-considerations/ to get the picture what keeping a structure built in traditional ways cost to the operator. For housing purpose you need to match the land condo administration pricepoints – marine steelbuilding especially Cruiseships and their rule coding are factors 100 or more away from this pricepoint. Only floating concrete shell and honeycomb technology can match the necessary price per squaremeter and decades of service life, necessary for a real estate development at the watersurface. This is the reason why cruiseships oil rigs barges and other marine steel structures are NEVER converted sucessfully into “floating condo real estate” the required maintanence costs are out of orbit the income created can not match the maintenance cost. Concrete structures solve that problem and put feasibility on floating suburban housing solutions.